Re: Root cause for ORA-00471

From: Mladen Gogala <gogala.mladen_at_gmail.com>
Date: Mon, 8 Jul 2024 19:41:28 -0400
Message-ID: <588bcb4b-ce30-495d-b16c-4c6b9f77e3e0_at_gmail.com>

For the redo log question (if 3 groups of 200MB each are enough) you can check the log switch frequency.  Oracle recommends trying to hit 4-5 redo log switches per hour. (ref: Can Not Allocate Log Doc ID 1265962.1)

So if your redo log switches are around 15 every hour (for example), they're not large enough.

You can check your log switches with this script:

Script To Find Redolog Switch History And Find Archivelog Size For Each Instances In RAC (Doc ID 2373477.1)

Depending on your hardware age and storage, don't be afraid to have large redo logs.  On a very busy medical system I used to work on, we had 2G redo logs to get the redo log switches down to 4-5 per hour.

HTH,

Chris

There is a problem with large redo logs: standby databases. If you have a remote standby, then your archives go over the WAN. And that might be problematic with a slow network. One of my previous employers used to have the primary in NYC and the standby in Louisville, KY. The WAN was slower than 1Gb/sec, so 2GB redo logs were out of the question. I had to live with approximately 10 - 15 switches per hour.

-- http://www.freelists.org/webpage/oracle-l Received on Tue Jul 09 2024 - 01:41:28 CEST